new rhetoric from north korea's young leader tonight. That country's top lawmakers heating today, kim jong-un with them. And then afterward, relacing a statement, calling their nuclear weapons, quote, their nation's life. Tonight, south of the border, they are taking this very seriously and abc's chief low gal affairs correspondent martha raddatz is in seoul, south korea, for us this evening. Martha? Reporter: Tonight, in north korea, it's volatile leader, kim jong un, has given no indication he will stop his dangerous provocation, with the regime saying its nuclear weapons are "the nation's life," that would not be traded for "billions of dollars." This coming just 24 hours after kim declared a state of war with its neighbor near in south korea. In the capital, seoul, just 35 miles from the border with the north, there is a sense of unease. "I am in the military," says this young man. "I feel this personally." The threats have been coming almost every day and each day, become more menacing. The threat of missile strikes on the u.S. Invading armies into south korea. And nuclear attacks. North korea has always made threats, but they are far more serious coming from a young, unpredictable leader. There's always that, even however small that may be, that ibility of miscalculation. He's been making a lot of threats, bricks brinksmanship and to follow that up, he does something, let's say bombing one of our lie laislands. It could escalate gradually or very rapidly. Reporter: The u.S., Which launched two nuclear-capable b-2 stealth bombers last week to carry out a practice bombing run less than 50 miles from north korea, says it will continue to respond to provocation. The u.S. Will not say specifically what those counter-provocation measures may be. But an indication of how serious they are? The pentagon says they hope they never have to put them into effect. David?

This transcript has been automatically generated and may not be 100% accurate.

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